The Opitha Tren system existed within the Mid Rim, specifically within the region of the freestanding subsectors. This system was the native habitat of the sentient Tren species.
The StarWars.com Online Companion, a supplement to the 2009 reference book The Essential Atlas, was the first appearance of the Opitha Tren system. It was located at grid coordinates J-15. According to Jason Fry, who co-authored The Essential Atlas, in a statement made on the Jedi Council Forums of TheForce.net, the creation of Opitha Tren served a "bookkeeping" function. This ensured that each sector listed in the Online Companion had at least one associated system, even though the Online Companion does not explicitly assign Opitha Tren to any particular sector.